Miniature growth chambers for the study of environmental conditions in vitro

Miniature (65-L) growth chambers, designed and tested to study environmental conditions affecting in vitro culture, provide an accurate and inexpensive method to perform multifactorial experiments under these conditions. Temperature control was achieved by an electronic device combined with a heating cable and a heat exchanger (water to air). Two-dimensional temperature variations in the chamber were within 1 °C of the set point temperature. Nine chambers were placed under photosynthetic photon flux (PPF) of 80, 125 and 250 μmol m −2 s −1 and CO2 concentrations of 330, 1650 and 3000 μL L −1 . Gas concentrations in both the chambers and the test tubes with in vitro cultures were monitored and fresh weight accumulation of raspberry (Rubus idaeus), strawberry (Fragaria × ananassa) and asparagus (Asparagus officinalis) cultures were recorded during a growth experiment. Carbon dioxide accumulation in the culture tubes during the night and subsequent depletion during the day indicated CO 2 fixation enhancement with CO 2 enrichment, which was more pronounced after 4 wk of growth. Fresh weight accumulated significantly under high CO 2 enrichment. Temperatures during the day were slightly higher in the test tubes (1 ± 0.3 °C) than in the chamber.Key words: Light intensity, temperature, carbon dioxide, tissue culture